High-damage tolerant alloy product in particular for aerospace applications

Abstract

The invention relates to an aluminium alloy wrought product with high strength and fracture toughness and high fatigue resistance and low fatigue crack growth rate, and having a composition for the alloy comprising, in weight %, about 0.3 to 1.0% magnesium (Mg), about 4.4 to 5.5% copper (Cu), about 0 to 0.20% iron (Fe), about 0 to 0.20% silicon (Si), about 0 to 0.40% zinc (Zn), and Mn in a range 0.15 to 0.8 as a dispersoids forming element in combination with one or more of dispersoids forming elements selected from the group consisting of: (Zr, Sc, Cr, Hf, Ag, Ti, V), in ranges of: about 0 to 0.5% zirconium (Zr), about 0 to 0.7% scandium (Sc), about 0 to 0.4% chromium (Cr), about 0 to 0.3% hafnium (Hf), about 0 to 0.4% titanium (Ti), about 0 to 1.0% silver (Ag), the balance being aluminium (Al) and other incidental elements, and whereby there is a limitation of the Cu—Mg content such that −1.1[Mg]+5.38≦[Cu]≦5.5. The invention further relates to a method of manufacturing such a product.

1. An aluminium alloy wrought product with high strength and fracture toughness and high fatigue resistance and low fatigue crack growth rate, said alloy consisting of, in weight %:
 Cu and Mg in a range which falls within a graphical box defined by the corner points:
 Corner point A is 0.45 wt % Mg, 5.35 wt. % Cu, 
 Corner point B is 0.75 wt % Mg, 5.35 wt. % Cu, 
 Corner point C is 0.75 wt % Mg, 5.0 wt. % Cu, 
 Corner point D is 0.45 wt % Mg, 5.20 wt. % Cu, 
 
 Fe <0.20, 
 Si <0.20, 
 Zn about 0.38 to <0.4, 
 Ag 0.32-0.48, 
 and Mn in a range of 0.15 to 0.31 and Cr in a range of 0.05 to 0.30 as dispersoid forming element elements in combination with one or more optional dispersoids forming elements selected from the group consisting of: 
 Sc <0.7, 
 Hf <0.3, 
 Ti <0.4, 
 V<0.4, 
 and the balance being aluminium and other impurities or incidental elements, wherein the alloy is substantially free of Zr. 
 
     
     
       2. An aluminium alloy wrought product according to  claim 1 , wherein the Mn-content is in a range of 0.20 to 0.31%. 
     
     
       3. An aluminium alloy wrought product according to  claim 1 , wherein the Cr-content is in a range of 0.06 to 0.15%. 
     
     
       4. Aluminium alloy wrought product according to  claim 1 , wherein the product is in the form of a sheet, plate, forging or extrusion for use in an aircraft structure. 
     
     
       5. Aluminium alloy wrought product according to  claim 1 , wherein the product is fuselage sheet, upper wing plate, lower wing plate, thick plate for machined parts, forging or thin sheet for stringers. 
     
     
       6. Aluminium alloy wrought product according to  claim 1 , wherein the product is in the form of a plate product having a thickness in the range of 12 to 76 mm. 
     
     
       7. An aluminium alloy wrought product according to  claim 1 , wherein the alloy product has a temper selected from the group consisting of T3, T351, T352, T36, T3x, T4, T6, T61, T62, ^T6x, T651, T652, T87, T89, and T8x. 
     
     
       8. An aluminium alloy wrought product according to  claim 1 , wherein the alloy product is aircraft fuselage sheet. 
     
     
       9. An aluminium alloy wrought product according to  claim 1 , wherein the alloy product is aircraft lower wing plate. 
     
     
       10. An aluminium alloy wrought product according to  claim 1 , wherein the alloy product is aircraft upper wing plate. 
     
     
       11. Aluminium alloy wrought product according to  claim 1 , wherein the alloy product is thick plate having a thickness of 63 to 280 mm for machined structures. 
     
     
       12. An aluminium alloy wrought product according to  claim 7 , wherein the alloy product is aircraft fuselage sheet. 
     
     
       13. Aluminium alloy wrought product according to  claim 7 , wherein the alloy product is selected from the group consisting of aircraft lower wing plate and aircraft upper wing plate. 
     
     
       14. An aluminium alloy wrought product according to  claim 7 , wherein the alloy product is a thick plate having a thickness of 63 to 280 mm for machined structures. 
     
     
       15. An aluminium alloy wrought product according to  claim 1 , wherein the alloy is substantially free of V to have <0.005% V. 
     
     
       16. An aluminium alloy wrought product according to  claim 1 , wherein
 Cu and Mg is in a range which falls within a graphical box defined by the corner points:
 Corner point A is 0.45 wt % Mg, 5.35 wt. % Cu, 
 Corner point B is 0.75 wt % Mg, 5.35 wt. % Cu, 
 Corner point C is 0.75 wt % Mg, 5.0 wt. % Cu, 
 Corner point D is 0.55 wt % Mg, 5.20 wt. % Cu. 
 
 
     
     
       17. An aluminium alloy wrought product according to  claim 16 , wherein the one or more optional dispersoids forming elements is selected from the group consisting of:
 Sc <0.7, 
 Hf <0.3, 
 Ti <0.4, and 
 V <0.4. 
 
     
     
       18. An aluminium alloy wrought product according to  claim 1 , with the proviso that Cu is not less than 5.09 wt. %, wherein the Mn-content is in a range of 0.20 to 0.31%. 
     
     
       19. An aluminium alloy wrought product according to  claim 1 , wherein the Zn-content is in a range of 0.38 to <0.4%. 
     
     
       20. An aluminium alloy wrought product according to  claim 1 , consisting of, in weight %:
 Cu and Mg in a range which falls within a graphical box defined by the corner points:
 Corner point A is 0.55 wt % Mg, 5.35 wt. % Cu, 
 Corner point B is 0.75 wt % Mg, 5.35 wt. % Cu, 
 Corner point C is 0.75 wt % Mg, 5.0 wt. % Cu, 
 Corner point D is 0.55 wt % Mg, 5.20 wt. % Cu, 
 
 Fe <0.20, 
 Si <0.20, 
 Zn about 0.38 to <0.4% 
 Ag 0.32 to 0.41%, 
 Mn in a range of 0.28 to 0.31 
 Cr in a range of 0.05 to 0.30 and 
 one or more optional dispersoids forming elements selected from the group consisting of:
 Sc <0.7, 
 Hf <0.3, 
 Ti <0.4, 
 V <0.4, 
 
 and the balance being aluminium and other impurities or incidental elements, wherein the alloy is substantially free of Zr. 
 
     
     
       21. The aluminium alloy wrought product according to  claim 1 , wherein the Mn-content is in a range of 0.15 to 0.28 wt %. 
     
     
       22. The aluminium alloy wrought product according to  claim 1 , wherein the Mn-content is in a range of 0.15 to 0.25 wt %. 
     
     
       23. The aluminium alloy wrought product according to  claim 1 , wherein the Mn-content is in a range of 0.15 to 0.20 wt %. 
     
     
       24. Method of producing a high-strength, high-toughness AA2000-series alloy product having a good damage tolerance performance, comprising the processing steps of:
 a) casting an ingot having a composition according to  claim 1 ; 
 b) homogenising and/or pre-heating the ingot after casting; 
 c) hot working the ingot into a pre-worked product; 
 d) optional reheating the pre-worked product and either, 
 e) hot working and/or cold working to a desired workpiece form; 
 f) solution heat treating said formed workpiece at a temperature and time sufficient to place into solid solution substantially all soluble constituents in the alloy; 
 g) quenching the solution heat treated workpiece by one of spray quenching or immersion quenching in water or other quenching media; 
 h) optionally stretching or compressing of the quenched workpiece; 
 i) ageing the quenched and optionally stretched or compressed workpiece to achieve a desired temper.